HOOSAC TUNNEL, in the towns of Adams and Florida, in Berkshire County, in Massachusetts, and piercing the Hoosac Mountain. It is on what is now known as the Boston and Maine Railroad, the route from Boston to Troy, N. Y., by way of Greenfield. From the west entrance of the tunnel to Troy is 54 miles; from the east entrance to Boston, 137 miles. The tunnel is nearly five miles in length, the longest tunnel in the United States and with the exception of the Rogers Pass tunnel in British Columbia the longest on the continent. Before the general introduction of railroads, and, as early as 1825, the project was broached of making a canal across Massachusetts from Boston to the Hudson River. This plan was abandoned when railroads were built across the State. In 1851 the tunnel question had advanced so far that surveys of various routes were made and some experiments were begun. The work of tunneling began in 1856 and was completed in 1873, For so long a tunnel the ventilation is good owing to the shaft, 1,028 feet, sunk near the centre. The width is sufficient for two tracks. The total cost, including 39 miles of adjoining railroad, was about $13,000,000.